Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 58, Num. 5, 2010, pp. 781-783

Neurology India, Vol. 58, No. 5, September-October, 2010, pp. 781-783

Case Report

Primary spinal melanoma of the cervical leptomeninges: Report of a case with brief review of literature

Mukul Vij¹, Sushila Jaiswal¹, Awadhesh Kumar Jaiswal², Sanjay Behari²

¹ Department of Pathology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
² Department of Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India

Correspondence Address:
Mukul Vij
Department of Pathology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Raebareilli Road, Lucknow - 226 014, UP
India
mukul.vij.path@gmail.com

Date of Acceptance: 22-Jul-2010

Code Number: ni10214

PMID: 21045512

DOI: 10.4103/0028-3886.72209

Abstract

Keywords: Central nervous system, leptomeninges, primary melanoma, spinal

Introduction

Central nervous system (CNS) primary malignant melanoma accounts for approximately 1% of all melanomas. Primary spinal melanomas are even more unusual. Since the initial report by Hirschberg in 1906, only 40 cases have been reported. These include intramedullary or extramedullary, leptomeningeal and extradural lesions. ^{[1],[2],[3],[4],[5]} This also includes 14 cases with dissemination from primary CNS malignant melanoma. The prognosis is poor, however, primary spinal melanoma has a better prognosis than cutaneous melanoma. We present a patient with primary spinal melanoma of the cervical leptomeninges.

Case Report

A 40-year-old man presented with complaints of sudden-onset progressive pain in right shoulder and neck of six months duration. Three months later, he developed gradual-onset progressive weakness of right upper limb; followed by weakness of right lower limb since 2 months. He also complained of right upper limb heaviness since 2 months. There was no history of bladder or bowel complaints. Neurological examination showed motor power of 4/5 grade on the right side and normal power on the left side. Deep tendon reflexes were brisk on the right side. Right plantar was extensor and left plantar flexor. Spinal tenderness against C2-C3 was noticed. Magnetic resonance imaging (MRI) spine revealed a well-defined round intradural extramedullary lesion measuring 2.1×1.9×1.5 cm against C1-C2. The lesion was hyperintense on T1 [Figure - 1]a and heterointense on T2 [Figure - 1]b images. There was intense contrast enhancement [Figure - 1]c. C1-C3 laminectomy with removal of posterior rim of foramen magnum and excision of lesion was performed. The tumor was attached to dura and had to be sharply incised to separate it. Duroplasty was done. Postoperatively, the patient did not experience any neck or shoulder pain and remains neurologically intact. He has not received adjuvant chemotherapy or radiation therapy. Subsequent evaluations over a period of 1 year by oncologists failed to find any other melanotic lesions or primary melanoma. Repeated magnetic resonance imaging of the craniospinal axis has provided normal results.

Grossly the surgical specimen submitted for histology measured 2.2×2.1 cm. It was blakish in colour. The tissue was fixed in 10% buffered formalin for 12 hours and processed for routine histology. Paraffin sections were stained with hematoxylin and eosin, Masson Fontana for melanin, and potassium permanganate bleach for melanin. Based on light microscopic examination, representative sections were selected for immunohistochemistry for HMB-45, S-100 and glial fibrillary acidic protein (GFAP). The histology of the tumor showed a solid growth [Figure - 2]a. The tumor cells were arranged in sheets, ill-defined fascicles and nests and displayed a moderate grade of cellular and nuclear pleomorphism and mitoses with abundant pigment in the cytoplasm [Figure - 2]b. The nuclear features were better appreciated after melanin bleach [Figure - 2]c. The pigment was positively stained with Masson Fontana [Figure - 2]d. The tumor cells were positive for HMB-45 [Figure - 3]a, and for S-100 [Figure - 3]b.

Discussion

Primary melanocytic neoplasms of the CNS are uncommon. They can be diffuse or circumscribed, benign or malignant. Diffuse lesions such as melanocytosis and melanomatosis generally occur in the setting of dermatologic syndromes (neurocutaneous melanosis, nevus of Ota). Localized lesions present as leptomeningeal masses and consist of a spectrum ranging from 'well-differentiated' melanocytomas to lesions of intermediate malignancy and overtly malignant melanomas. According to the Hayward classification, ^[6] the diagnosis of primary spinal cord melanoma is based on the absence of melanoma outside the CNS, the absence of this lesion at other sites in the CNS, and histologic confirmation of melanoma. According to these classification criteria, our patient had a primary malignant melanoma of the spinal cord. This lesion occurs most often at middle age and can affect both genders equally. ^{[1],[2],[3],[4],[5]} The presenting symptoms of this lesion are predominantly those of spinal cord compression. ^[5],[7]

Radiological studies may not be specific, especially in the absence of primary disease. MRI may offer some indication of a melanotic lesion, but the rarity of a primary melanotic lesion in the CNS most often precludes the preoperative radiological diagnosis of this lesion. According to most descriptions, the MR imaging pattern of spinal melanoma includes signal hyperintensity on T1-weighted images and signal isointensity or hypointensity on T2-weighted images. ^[1],[8] Pattern of melanoma on MRI depends on content of melanin, as well as acute or chronic intratumoral hemorrhages and fat deposits. ^[8]

Pathological examination and immunohistochemistry of the primary spinal melanoma are critical to diagnosis and distinguish it from other different nervous system tumors undergoing melanization, such as meningioma, schwannoma, medulloblastoma and gliomas. ^[8] There is little evidence to support the existence of true melanotic meningioma, although rare melanotic colonization of meningiomas has been reported. From a combined pathological and clinical point of view, the principle differential is between melanocytoma and melanoma. ^[8] Melanomas are more pleomorphic, have more anaplastic nuclei than melanocytoma and often demonstrate tissue invasion and necrosis. ^[8] It is obviously important to determine if the melanoma is primary or secondary. Absolute determination is only approached by a thorough examination at autopsy, including sectioning of the eyes. Even then, the possibility of previous regression of a primary site cannot be eliminated entirely.

In the present case, the cytological features were quite typical of malignant melanoma. Immunoreactivity for the HMB-45 melanoma antigen and S-100 further supports the diagnosis. HMB-45 is a useful marker for melanocytic differentiation in a neoplasm, because it indicates active melanosome formation. ^[9] S-100 is expressed by cells with melanocytic differentiation but is also found in other neuroectodermal cell types. As anticipated, GAFP was nonreactive.

Malignant melanomas are considered to be highly aggressive and radio-resistant tumors with poor prognosis. Beresford reported only 1 of 37 patients with intracranial melanoma responding to radiation therapy. ^[10] It has been suggested that primary spinal melanoma exhibits slow progression, and the tumor is less aggressive than the more common melanoma of the skin with metastases to the CNS. Metastatic melanomas grow rapidly and usually lead to fatal outcome in less than 6 months.

References

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